מדרש על איוב 40:16

R. Juda, in the name of Rab, said: "All that the Holy One, praised be He, created, was male and female, and also the leviathan — the flying serpent male, and the crooked serpent female; and if they should have intercourse they would destroy the world. What did His Holy One, praised be He! do [to prevent this]? He made the male impotent, and killed the female and salted it for the righteous in the future world, as it is said (Ib.) And He will slay the crocodile, etc. And also (Ps. 50, 10) the cattle upon a thousand mountains. He created them male and female, and if they should have intercourse, they would destroy the world. Therefore, the Holy One, praised be He! rendered the male impotent and rendered cool the female, and preserved it for the righteous in the future world, as it is said (Job 40, 16) Only see [how great] is the strength in his loins, referring to the male, and his force in the muscles of his belly, referring to the female. But why did He not render cold the female of the leviathan also? Because a salted female has a better taste. And why did He not salt the females of the cattle in question? Salted fish gives a good taste, but salted meat does not.